There are questions in other reviews below about the "missing" 1950-1951 season episodes.
According to another webpage which has a lot of info about the show, there was in fact *no* 1950-1951 season for M&L on the radio:
http://www.digitaldeliftp.com/digitaldelitoo/dd2jb-Martin-and-Lewis.html
(If clicking that link doesn't work, you may be able to reach the webpage by Googling "The Definitive Martin and Lewis Radio Log")
NBC Radio aired Season One of the Martin and Lewis Show in 1949-1950 and Season Two in 1951-1952. The hiatus came about because NBC was disappointed in the radio show's first-season ratings and was having difficulty securing sponsors (a subject of some first-season jokes on the show), and the show had very high production expenses; the network was losing too much money on it. M&L were unwilling to renegotiate their contract to reduce production costs, so NBC decided not to renew the radio show for what would have been a second season beginning in mid-1950.
Instead NBC moved M&L for fall 1950 to the rapidly-growing TV side where Jerry's physical comedy figured to play better. M&L were among four rotating co-hosts of the Colgate Comedy Hour. That show did better, and their movie career took off, and NBC and M&L agreed to terms for two more seasons on the radio that included sponsorship after the unusual one-year hiatus beginning in mid-1951. They also continued to co-host the Colgate Comedy Hour on TV for several more seasons.
By mid-1953 when the M&L radio show was not renewed for a fourth season, radio generally was in ratings free-fall compared to TV. During the mid-1950s, many long-running expensive radio shows transitioned to TV (see Jack Benny), or slashed production costs (see Fibber McGee and Molly), mainly because advertisers saw better bang for their marketing buck on TV.
As you can tell by show dates, there are M&L radio episodes that have not survived, but there is no entirely missing season.
Some old-time radio comedies aren't very funny anymore to me, but many of the M&L episodes, particularly in Seasons Two and Three when the show consistently used writers Ed Simmons and Norman Lear (who also wrote M&L movie scripts) still hold up quite well today in my opinion.
The early episodes had their moments but are overall more miss than hit for me and apparently for many critics and listeners back at that time as well, as the show got off to a slow start in translating Dean and Jerry's very successful nightclub act to radio.
THANK YOU zacandan for sharing these shows with everyone.